1. Technical Field
The present invention relates to an image forming apparatus.
2. Related Art
As an image forming apparatus which performs color printing, there is a tandem type apparatus which includes, for each color, an image forming part (a photoconductor, an exposure device, and the like) that transfers a toner image of each color onto paper.
In this tandem type image forming apparatus, the image forming part for each color (Y (yellow), M (magenta), C (cyan) and K (black) performs a printing operation onto a paper sheet, and a color image is formed by toner images of four colors.
Therefore, in case that transfer timing onto a transfer belt is slightly different among the image forming parts for the respective colors due to change of temperature and change with time, printing is performed in a state where only a specified color in one image is misaligned, so that a so-called misregistration arises.
As technology of registration adjustment for correcting this misregistration, there is technology in which an image forming part for each color forms on a transfer belt a registration adjustment patch, a sensor detects the amount of deviations in the position of each color registration adjustment patch on the transfer belt from a reference position, and the writing timing at the image forming part is changed so that the amount of this misregistration can be eliminated.